Aldehydes Crotonaldehyde Formaldehyde

In industrial processes, formaldehyde, acetaldehyde and, to a lesser extent, acrolein are used as aldehydes crotonaldehyde can also be employed for the synthesis of pyridines. 

CAUTION As described later in Chapter 2, the reaction of formaldehyde with hydrogen chloride has been shown to lead to the spontaneous production of the now known carcinogen te(chloromethyl) ether. In addition, other aldehydes (crotonaldehyde, acetaldehyde, acrolein, etc.) are also toxic [7], Toxicity limits for some representative compounds in air... 

Skog, E. A toxicological investigation of lower aliphatic aldehydes. I. Toxicity of formaldehyde, acetaldehyde, propionaldehyde and butyraldehyde as well as of acrolein and crotonaldehyde. Acta Pharmacol, 6 299-318, 1950. 

Among the aldehydes and ketones tested acetone was least toxic, formaldehyde, butyraldehyde, and crotonaldehyde next, and mesityl oxide most toxic. In this group of compounds temperature was a major factor, both formaldehyde and mesityl oxide being much more toxic at 40 than at 25 C. None were outstanding as cholesterol solvents, but mesityl oxide was the best it penetrated nematodes the most easily and killed in the lowest concentrations. 

Polarographic methods of analysis of the derivatives of formaldehyde and crotonaldehyde without chromatography were developed. Analysis by HPLC was later considered so as to achieve greater resolution between the individual aldehydes and potential interferences. Methods validated using HPLC analysis include acetaldehyde and furfural. Tests indicated that HPLC analysis may be applicable to the Girard-T derivatives of other aldehydes, such as formaldehyde, propionaldehyde, and benzaldehyde. 

Fig. 5.3. Gas chromatogram of 2,4-dinitrophenylhydrazones of ten aliphatic aldehydes. Peaks 1 = formaldehyde 2 = acetaldehyde 3 = propionaldehyde 4 = acrolein 5 = isobutyraldehyde 6 = n-butyraldehyde 7 = isovaleraldehyde 8 = n-valeraldehyde 9 = crotonaldehyde 10 = n-capronaldehyde. For conditions see text. (Reproduced from / Chromatogr., 120 (1976) 379, by courtesy of Y. Hoshika.)...

If R=H (i.e., formaldehyde), reaction 7.6 occurs with high yield on both TiO and UO surfaces, while if R=CH3 or higher, the condensation of two aldehyde molecules competes and results in the formation of unsaturated higher aldehydes such as crotonaldehyde (CHjCH=CHCHO) from acetaldehyde (CH3CHO) (7.7) [63]. 

Several solid-liquid two-phase systems have been described powdered KOH in THF or DMF, Ba(OH)2 in moist dioxane, K2CO3 in water or D2O or anhydrous solvents, Na2CO3 in moist THF and NaHCO3 in water. The system using aqueous 6-9 M K2CO3 solution appears as the most promising. This new technique provides routinely good yields of functional olefins from aldehydes (Scheme 6.48). It allows the use of functional aldehydes without protection or aqueous stabilized solutions of unstable pure aldehydes without previous isolation (formaldehyde, crotonaldehyde). 

ALDEHYDE CROTONIQUE (French) (123-73-9) see (E)-crotonaldehyde. ALDEHYDE FORMIQUE (French) (50-00-0) see formaldehyde. 

In testing the ciliatoxicity of cigarette MSS aldehydes to clam gill cilia, Wynder et al. (4330) reported that formaldehyde, acrolein (propenal), and crotonaldehyde (2-butenal) showed the highest toxicity. They also reported that acrolein was about twice as ciliatoxic as phenol in the clam gill cilia test [see also Wynder and Hoffmann (p. 253 in (4332)]. In addition to then-aldehyde ciliatoxicity results, Wynder et al. (4330) also noted the serious error introduced into the results obtained in their study of the ciliatoxicity of low molecular weight acids in tobacco smoke. 

Brunnemann et al. (500) detemiined several volatile aldehydes and ketones in tobacco headspace and tobacco smoke by derivatization with 2,4-dinitrophenylhydrazine. Tobacco smoke carbonyl components identified included Formaldehyde, acetaldehyde (1000 pg/cig), propionaldehyde (propanal), acrolein (propenal), isobutyraldehyde (2-methylpropanal), crotonaldehyde (2-butenal), methacrolein (2-methylpropenal), benzaldehyde (1 pg/cig), and acetone. 

Hoffmann and Hoffmann (1740, 1741) in their lists of 60 tumorigenic components of tobacco and tobacco smoke included only two aldehydes - formaldehyde and acetaldehyde. Crotonaldehyde (2-butenal) include in the 1990 Hoffmann-Hecht list (1727) was omitted from the Hoffmann-Hoffmann (1740), an omission that paralleled the 1994 OSHA list (2825). 

Carbonyl compounds are probably present at low levels in all air samples (Fung and Grosjean, 1981). A great variety of combustion processes produce aldehydes they are particularly abundant in wood smoke, and have also been identified in the products of combustion of natural gas and fuel oil, and in engine exhaust samples. It is likely that they are relatively long-lived intermediates in atmospheric photooxidation reactions. Formaldehyde (CH2O), for example, is always an obligatory intermediate in the conversion of methane to CO2. In nearly all air samples so far examined, formaldehyde has been the most abundant aldehyde, with acetaldehyde, pro-pionaldehyde, acrolein, benzaldehyde, crotonaldehyde, and furfural sometimes present at much lower concentrations (Kuwata et al., 1979 Penkett, 1982 Zhou and... 

Mitoma C. and Leeper L. Federation Proc. 13, 266 (1954)) separated the enzyme system into two enzymes which together hydroxylate phenylalanine in the presence of DPN and an aldehyde or alcohol. Effective compounds are acetaldehyde, propion-aldehyde, butyraldehyde, benzaldehyde, crotonaldehyde, propanol and benzyl alcohol. Formaldehyde, ethanol, glucose, ribose, glyoxylate and xanthine were inactive. 

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